Light energy emitters, including lasers, and in particular semiconductor diode lasers, flash lamps, halogen and other filament lamps, etc., are finding increasing application in medical, industrial, research, governmental and other applications. For many of these applications, the light energy is to be delivered at a selected depth in a light scattering medium. Because of the scattering, only a fraction of the light energy delivered to the surface of the medium reaches the target area, with much of the remaining energy being refracted out of the medium and dissipated in the surrounding atmosphere. For a highly scattering medium such as skin, as much as 50-80 percent of the incident energy may be lost due to this back scattering effect, requiring more powerful light energy emitters/lasers or a larger number of emitters/diodes lasers (where diode lasers are used), or requiring that light energy be delivered over a much smaller area, in order to achieve a desired fluence at a target. Utilizing a head with a more powerful emitter/laser or utilizing a larger number of and/or more powerful emitters/diode lasers makes the head larger and more expensive and increases the heat management problems resulting from use of the head. Concentrating the beam to achieve higher fluence with smaller spot size or aperture adversely affects the depth in the medium which can be reached by the light energy and can significantly increase the time required to perform a given procedure.
U.S. Pat. No. 5,824,023, to Rox Anderson, teaches one way of dealing with the reflection problem with certain laser or other light energy emitting devices. However, the technique of this patent also results in small spot sizes and is not readily adaptable for use in certain applications, such as in laser diode heads. An improved technique is therefore required to permit optimum utilization of the light energy from light energy emitting devices in general, and from laser diodes or laser diode bars of a laser diode head in particular, by recycling or reusing light scattered from the surface of the irradiated medium and directing it back toward a desired target area in the medium.
A related problem involves heat management when using a laser diode head, or other head containing light energy emitters, and in particular the ability to utilize a common cooling element to cool both the laser diodes/light energy emitters and the surface of the medium being irradiated. Surface cooling can be required in various applications, particularly medical applications, since laser energy being delivered at a depth in the medium, for example a patient's skin, must pass through the surface of the medium, for example the epidermis of a patient's skin, in order to reach the target area. Heating of the medium surface can cause damage at the surface if suitable cooling is not provided. Prior art systems have either not provided cooling for the medium surface or have required separate cooling elements for the diodes and the medium.